MySQL查询，在其中一个表中组合了两个表和两列

Question

我正在尝试编写一个SQL查询，在其中一个表中组合了两个表和两个列。 所以，我有两张桌子

表： Items

ID          Material           Shape

1           glass              jar
2           plastic            bottle
3           cardboard          box
4           glass              bottle

表： Diary

ItemID      UserID      Quantity

2           1           1
1           1           3
3           1           2
2           1           5
4           1           1

UserID = 1预期输出（按combined quantity排序）：

Combined column values       Combined quantity

plastic bottle               6
glass jar                    3
cardboard box                2
glass bottle                 1

有人能以正确的方式指导我吗？

Answer 1

我认为这只是一个join和group by ：

select concat_ws(' ', i.material, i.shape) as combined,
       sum(d.quantity) as combined_quantity
from items i left join
     diary d
     on d.itemId = i.id
group by combined
order by combined_quantity desc;

Answer 2

询问

select Material+SPACE(1)+ SHAPE [Combined column values ], 
SUM(QUANTITY) [Combined quantity]
from Items 
left join diary on Items.itemiD = diary.itemID  
GROUP BY ITEMS.itemiD, Material, SHAPE 

产量